Monitoring device for printer

ABSTRACT

A monitoring device is provided for a printer, especially a sheet-fed offset printer. The printer has a controller that records the signals of signal transmitters in the individual units of the printer, through which command signals for actuators/drives connected to the control can be generated as a function of the signal state, and a monitoring computer that additionally records the signal states of the signal transmitters and causes the switching off of actuators/drives. In the monitoring device, the signal states of the signal transmitters (G) of the printer units are fed to several slave computers (S), which are connected to each other via a monitoring bus (UB) and to a monitoring master (UM) connected upstream from the monitoring computer (UR). The actuators/drives (A) are connected to respective ones of the slaves (S) and can be switched off by the slaves in response to a command sent by the monitoring master (UM) via the monitoring bus (UB).

FIELD OF THE INVENTION

The invention relates to a monitoring device for monitoring theoperation of a printer, such as a sheet-fed offset printer.

BACKGROUND OF THE INVENTION

Sheet-fed offset printers have a number of units, such as the feeder,delivery device, printing groups, coating and processing devices.Different operating elements in the form of control switches areprovided to operate these individual units and the printer as a whole,through which machine operation, certain operational functions, etc.,can be initiated. The moving elements, such as cylinders and rollers,are protected by protection elements movable for maintenance purposes,in order to prevent the operator from being exposed to danger from arunning machine due to an open protection circuit. The protectionelements are protected by sensors and switch elements designed as limitswitches. The signals of the operating elements in the individual units,as well as the sensors and switches that protect the individualprotection systems, are connected to one or more stations, forming thecontroller of the printer, which are preferably configured as acomputer. A controller, which consists of at least one computer and thatrecords the signal states of the different control elements andprotective switches, is known from DE 43 27 848 A1 and EP 0 243 728 A2.DE 195 27 089 A1 and 195 20 918 A1 describe the individual units of thestations designed as a computer and connected to the printer, whichcombine to form the controller of the printer.

As is known from DE 43 27 848 A1 and EP 0 243 728 A2, certain functionsof a printer must be protected redundantly, i.e., the activation of acontrol element or the opening of a protection system causes theimmediate shutdown of the corresponding drive, especially the main driveof the printer. As a result, the signals of the corresponding operatingelement and the switches that protect the protection system are fed bothto the controller and, parallel to it, to a monitoring device configuredas a computer. Switching of the drive or drives as a function of thesignal state then occurs both via the controller and via the monitoringdevice. Shutdown therefore also occurs during failure of the controller.

The variety of operating elements and safety elements (switches,sensors) results in high cabling expense due to the redundant monitoringof the signal transmitters. The high cable expense also hinders thesearch for errors during cable defects or malfunctions in thecorresponding plug-in connectors.

The large number of operating and protection elements to be monitored(switches, sensors) also causes a high computer load on the monitoringsystem. This is especially true, since it must be guaranteed by thecontroller and by the monitoring system that a specific reaction,especially shutdown (stopping) of the printer, occurs within astipulated interval at specified signal states.

OBJECTS AND SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the invention to provide animproved monitoring device for a printer, especially a sheet-fed offsetprinter, that enables easy error identification in the event of amalfunction, while avoiding the aforementioned shortcomings of prior artmonitoring devices.

The monitoring device according to the invention has a bus system, viawhich several computers that enter the signal states of the operatingelements, switches and sensors and function as slaves are connected to amaster computer. Commands to enter the input (signal state) arerepeatedly sent to the individual slaves via the bus system by themaster connected to the actual monitoring computer. In response to acommand, the individual slaves send an indicator of the inputs presentin them (signal states of the operating elements, switches, sensors).The master, connected after the monitoring computer, thus obtains, oneach query, an indication of all the input states in the individualunits to which the slaves of the monitoring device according to theinvention are assigned. The monitoring computer then generates, from itsoverall input indication, switching commands for the drives andactuators being monitored. If a state results from the input indicationentered by the master, based on which a drive or actuator, andespecially the main drive of a printer, is to be stopped, this commandis sent via the bus system to the corresponding slave in thecorresponding unit. The slave receiving this command then causesswitching off or stopping of the actuator/drive.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawing, in which:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram showing a sheet-fed offset printer havinga monitoring system in accordance with the invention.

While the invention is susceptible of various modifications andalternative constructions, a certain illustrative embodiment thereof hasbeen shown in the drawing and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed. On the contrary, the intentionis to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF PREFEFFED EMBODIMENTS

An embodiment of the invention will now be explained with reference tothe single drawing. The drawing shows, in a generally schematic form, asheet-fed offset printer D with a decentralized control, as well as themonitoring system made up of a master UM and slaves S.

The sheet-fed offset printer D as depicted in the figure has a feeddevice, a delivery device, and printing groups. Stations ST, configuredas a computer and forming the overall controller, are connected to theindividual units of this printer D. The entering of signals of signaltransmitters G arranged in, for example, the delivery device thus occursvia the station (computer) ST connected to the delivery device of theprinter D. In the interest of clarity, only one signal transmitter Gconnected to a station ST is shown in the figure. The signaltransmitters G in the individual units of the printer D can be sensors,switches, operating elements, control switches, etc.

Control of actuator/drives A arranged in the corresponding unit alsooccurs in the individual units in the printer D via the individualcomputers of the stations ST. Here again, for simplicity, only oneactuator/drive A connected to a station ST is shown.

The individual stations ST are connected to each other via a control busSB, so that switching operations corresponding to the sheet run can beperformed in the individual units of the printer D. The stations ST arealso connected via the control bus SB to the central control station LSof the printer D.

A slave S is connected as computer to each station ST of the printer D,which is connected via a common serial bus system UB to another computerUM, designed as a master. The master computer UM communicates with amonitoring computer UR. The signal transmitters G in the individualunits, as well as the actuators/drives A, in addition to communicatingwith the stations ST, also communicate with the slave S by means of acorresponding input card. An operating state of the signal transmitter Gcan therefore be recorded both by the control station ST and by theslave S.

The monitoring master UM connected to the monitoring computer URperiodically sends query commands to the individual slaves S via themonitoring bus UB. In response to the query, each of the slaves S entersthe signal states of the connected signal transmitters G via the inputcards. An indication of the signal states of transmitters G is sent backby each slave S via the monitoring bus UB to the monitoring master UM,so that the presence of permitted and/or unpermitted states can bedetermined via the monitoring computer UR from the indication of thesestate signals of all transmitters G. If the monitoring computer UR findsthat a protective grid is opened, for example, during the running of themachine, the monitoring master UM sends, via the monitoring bus UB, asignal to the corresponding slave (main drive), in order to stop theprinter. Switching off of the corresponding drive A then occurs via theslave S connected to it. Due to the fact that the monitoring computer URis connected via a monitoring master UM and the monitoring bus system UBto the slaves S assigned to the respective individual units of theprinter, a noticeable simplification in cabling expense is produced,since only one shielded line is necessary for the serial bus system. Asan additional advantage, a simultaneous indication of all the switchingstates of the operating elements, sensors, switches recorded by theslaves is available to the monitoring computer as the result of eachquery cycle. Therefore, interdependent switching states (signal states)can be determined, and the entire printer and the switching states ofsignal transmitters mounted on the printer can be monitored.

Since the switching on/off of actuators/drives in the event of amalfunction occurs through a slave of the monitoring system assigned tothe corresponding unit, measures adapted to the corresponding hazardoussituation being protected against can be introduced. Upon the opening ofa protection system between the individual printing groups, the slaveassigned to the main drive would shut down the printer drive in responseto a master command and therefore stop the operation of the printeritself. If, for example, only a protection system assigned to the inkduct is open during machine operation and print production, to avoid ahazardous situation (feed site), it may be sufficient merely to shutdown the corresponding drive (for example, the drive of the ductroller). Interruption of the entire printing process and thus ink flowinto the individual printing groups can be avoided in such a situation.Restarting of the machine with a correspondingly large number of wastedsheets is thus unnecessary. After closure of the correspondingprotection system and possibly acknowledgment by an operating person,the drive shut down by the monitoring system according to the inventioncan be switched on again, so that the ink flow malfunction, occurringonly briefly in the printing group, if at all, only causes a smallnumber of wasted sheets.

Switching off of the corresponding components occurs via the slave S ofthe monitoring system assigned to the unit. This slave S receives thecommand to shut down from the master UM assigned to the monitoringcomputer as a function of evaluation of the queried switch signal statesfed to the master. Individual switching off of actuators and drivesduring failure of one or more components of the control is thus possibleby the monitoring system according to the invention.

In a preferred embodiment of the invention, the slaves S assigned to themonitoring system monitor the cyclical query of the master UM via asoftware routine. If a query order from the master is absent within astipulated time interval (which can be caused, for example, by amalfunction in the bus system or a malfunction in the master), switchingoff of the actuator/drive assigned to the slave or the entire printer(main drive) occurs. Malfunctions in the bus system between the masterand the slaves can therefore be monitored, based on errors in signaltransmission.

In an alternative preferred embodiment of the invention, each slaveassigned to the stations of the unit additionally has a hardware timeoutsetup (watchdog). In addition to software monitoring of command signalscoming from the master, the bus that connects the slaves to the masteris also monitored. Here again, in the absence of a master signal withina stipulated time interval, shutdown of the prescribed actuators, drivesor the entire printer occurs.

Thus, software and/or hardware timeouts may be provided in theindividual slaves S, so that, in the absence of a corresponding querysignal from the monitoring master UM, the actuators/drives A can beautomatically shut down by the slave S.

What is claimed is:
 1. A monitoring device for a printer havingindividual units and a controller that includes a plurality of controlstation computers connected by a control bus and records signals ofsignal transmitters in the individual units and generates commandsignals for actuators/drivers of the printer based on the signals of thesignal transmitters, the monitoring device comprising: a monitoringcomputer for recording signals of the signal transmitters and causingthe actuators/drivers to switch off based on the signals of the signaltransmitters; a monitoring bus separate from the control bus; amonitoring master connected to the monitoring bus and connected to themonitoring computer; a plurality of monitoring slaves connected by themonitoring bus to the monitoring master for communications therewith,each monitoring slave assigned to a corresponding individual unit of theprinter and connected to receive signals of signal transmitters of saidcorresponding individual unit, said each monitoring slave programmed tosend an indication of the signals of the signal transmitters to themonitoring master in response to a state query and to switch offactuators/drives connected thereto in response to a command sent via themonitoring bus by the monitoring computer through the monitoring master.2. A monitoring device as in claim 1, wherein the monitoring bus is aserial bus.
 3. A monitoring device as in claim 1, wherein the monitoringmaster periodically sends the state query to the monitoring slaves viathe monitoring bus.
 4. A monitoring device as in claim 1, wherein themonitoring master is programmed to monitor indications of signal statessent by the monitoring slaves via the monitoring bus.
 5. A monitoringdevice as in claim 1, wherein said each monitoring slave switches offthe actuators/drives connected thereto when no state query from themonitoring master has been received within a timeout period.
 6. Amonitoring device as in claim 1, wherein said each monitoring slave isprogrammed to monitor whether the state query from the monitoring masterhas been received within a timeout period.
 7. A monitoring device as inclaim 5, wherein said each monitoring slave includes a hardware timeoutdevice for monitoring whether the state query from the monitoring masterhas been received within a timeout period.
 8. A monitoring device as inclaim 1, wherein the printer is a sheet-fed offset printer.